This invention relates to hand tools, and particularly to mechanisms for holding or gripping objects. More particularly, this invention relates to compliant pliers.
Traditional pliers of the type commonly found in the home or workplace are made of a rigid-body structure. The members that make up the rigid-body structure are stiff and are connected at various pivot points to gain mobility and create a mechanical advantage. Mechanical advantage is the advantage gained by use of a mechanism in transmitting force such as by manually gripping the handles of the pliers so that an object gripped by the jaws of the pliers is held tightly.
A compliant mechanism includes some portions that flex while the other portions remain rigid. Compliance generally is the ability of an object to yield elastically when a force is applied.
Early compliant pliers used living hinges to replace the pivot points found in traditional rigid-body pliers. These living hinges were very thin and therefore very flexible. Essentially, the early compliant pliers used rigid-body construction and simply replaced the conventional pivot pins with thin flexible living hinges. Unfortunately for users of such early compliant pliers, these thin living hinges lacked the ability to transmit substantial forces and often showed signs of stress marks, indicating a temporary disposable product.
What is needed is an improved compliant pliers that is easy to manufacture and able to transmit substantial forces. Such compliant pliers could be used for pinching, gripping, clamping, or holding a wide variety of objects.
In accordance with the present invention, pliers include an endless loop, a top jaw appended to the endless loop, and a bottom jaw appended to the endless loop. The endless loop includes in series a top grip handle, a spring segment, a bottom grip handle, and a compliant strip interconnecting the top and bottom grip handles. The spring segment interconnects the top and bottom grip handles.
Each of the top and bottom jaws are appended to the compliant strip to move with the compliant strip. The pliers further includes rolling means on the top grip handle for rolling on a contact portion of the bottom grip handle to translate the compliant strip longitudinally relative to the top and bottom grip handles in response to movement of the top grip handle toward the bottom grip handle as the pliers are squeezed by a user. This will cause the top jaw to move toward the bottom jaw to grip an object positioned between the top and bottom jaws.
In preferred embodiments, the endless loop and the top and bottom jaws are molded of a plastics material. Preferably, the compliant strip is somewhat U-shaped and has a nearly uniform thickness. It includes a top compliant segment coupled to the top grip handle, a bottom compliant segment coupled to the bottom grip handle, and a middle compliant segment interconnecting the top and bottom compliant segments. Illustratively, the middle compliant segment is curved and has a concave surface facing toward the top and bottom grip handles.
Illustratively, the spring segment is C-shaped and has a concave surface facing toward the concave surface of the middle compliant segment. The spring segment is configured to urge the top and bottom grip handles normally to a spread-apart position wherein the compliant strip appended to the top and bottom grip handles is moved, causing the top and bottom jaws to move apart to an object-receiving position.
By manually squeezing the top and bottom grip handles together against the restoring force generated by the spring segment, a user is able to roll a curved portion of the rolling means on the top grip handle along a curved contact portion on the bottom grip portion. This rolling action causes the compliant strip to flex or deform and such movement of the compliant strip causes the top and bottom jaws appended to the compliant strip to move toward one another to an object-gripping position.
The use of an endless loop in compliant pliers is advantageous in several respects. The endless loop is a closed-loop construction and provides a built-in automatic spring which functions to return the grip handles, compliant strip, and top and bottom jaws to neutral (stress-free) positions once the user releases the grip handles. The endless loop design also creates a moderate system resistance for enhanced user control and provides additional lateral stability. The endless loop design further protects flexural "pivots" from damage by limiting motion of the pliers components to a non-stressful range of motion.
Rolling longitudinal translating movement of contact engagement between contact portions appendant to the top and bottom grip handles is an improvement over pivot pins associated with traditional pliers. A rolling contact configuration can be varied easily by the pliers designer to change the mechanical advantage of the pliers without significantly altering the overall configuration of the compliant pliers. Merely by molding the compliant pliers to move the rolling contact members away from the jaws and toward the tails of the grip handles, it is possible to increase the mechanical advantage of the compliant pliers. The rolling contact design can also withstand large compressive forces generated by a user squeezing the grip handles without a significant loss of energy due to friction.
Compliant pliers including a compliant strip of the type supporting the object-gripping jaws and appended to the grip handles is an improvement over traditional pliers of the type using various pivot pins to create pivot points. This improved compliant strip design leads to higher force output and enhanced object gripping action at the jaws during use of the compliant pliers. It also makes it possible to use materials with superior mechanical properties to form the compliant pliers since the compliant strip need only have moderate flexibility.
There are many applications for one-piece compliant pliers in accordance with the present invention. For example, such pliers could be configured for use as a fish hook remover, forceps, or crafter's pliers. Also, it is well-suited for use as electronics and electricians' pliers and crimpers. The improved compliant pliers of the present invention is ideal for any application needing moderately high object-gripping forces with jaws capable of gripping delicate objects without damage to such objects.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.